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Author Topic: Spectro UV filter question  (Read 2806 times)
Jonathan Wienke
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« on: September 04, 2005, 11:05:02 AM »
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I have the non-UV filtered Eye-One spectrophotometer. IMO the UV filtered version isn't necessary, as better-quality papers don't have UV brighteners anyway. The illuminant in the EyeOne is an incandescent lamp with a fairly low color temp, and doesn't contain a huge amount of UV.

The color cast could go either way: If ambient light contains more UV than the Eye-One illuminant, the increased fluorescence will give the print a blue cast in that particular lighting. If ambient lighting contains less UV than the Eye-One illuminant, then the reduced fluorescence will give the print a yellow cast in that particular lighting. The rendering intent doesn't matter, papers with UV brighteners are going to be problematic because their apperance will differ significantly depending on the amount of ambient UV.

Rodney and Fraser are both correct; Rodney is referring to the appearance of the print during the measuring process, and Fraser is referring to the appearance of a print made with the resulting profile. It's no different than measuring the color patches on a bright blue desk surface, the blue will bleed through the paper and skew the patch measurements, and a profile built from such measurements will result in prints that have a pronounced yellow cast.
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digitaldog
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« Reply #1 on: September 05, 2005, 08:46:08 AM »
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If youíre using GMB software which intelligently handles the UV in software, you donít need the filter. But thereís still other products that could interface with the Eye-One that canít. The jury is still out about this issue. Most of us feel, based on building a heck of a lot of profiles that when UV is detected in software, the software does a really good job of handling it.

You can see the ugly effect if UV skews the profile but that can be edited out with a good editor that can handle the white point as ProfileEditor can with the GMB bundle. I have a number of Spectrophotometers, some with filters you turn on and off. Right now, with the Monaco DTP-70, the filter is off just for testing and Iím building profiles with PROFILER. So far so good.

You can measure the paper and if the b* value is a negative, itís a good sign you might be finding OB in the paper.

Andrew Rodney
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Andrew Rodney
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digitaldog
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« Reply #2 on: September 05, 2005, 01:41:38 PM »
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Quote from: Hermie,Sep. 05 2005,16:15
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About Monaco Profiler, when you look at the measuring devices that can be selected from within Profiler, there's the eye-one and the eye-one UV.Does it do something we don't know of?

What I really like about Profiler is the option to tweak the perceptual gamut compression.

In a thread on Rob Galbraith, Ethan Hansen wrote about the difference in measurement intervals between eye-one (10nm) and pulse (20nm + interpolation to 10nm). Do you thinks this is an issue in favor of the eye-one?

Herman
Iím not sure why two options for UV and non are there, it might be in the Eye-One SDK. Iíll see if I can find out from X-Rite why they do this. It might be necessary when the instrument is used for the display.

GMB has some tweaks to Perceptual tables as well (Logo Chroma Plus versus Colorful etc). They also let you play with how the profile deals with the neutrality of (or lack thereof) of the paper.

Iíve seen the comments by Ethan. I donít find the DTP-70 to produce inferior profiles compared to the iCColor or the Eye-One. Itís very fast and it has a habit of being a tad flaky but on output, I see no difference.

The Eye-One has many advantages in itís so flexible. Spot (canít do that with DTP-70), Projectors (hope), Displays (nope). Light sources. But it does make you work for your profiles. The DTP-70 is ideal for someone that is making lots of profiles and need incredible speed. Itís shockingly fast.
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Andrew Rodney
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Hermie
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« Reply #3 on: September 04, 2005, 10:30:39 AM »
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I'm going to upgrade my printer profiling package from CM2C colorimeter to eye-one photo.

GMB advises the version without UV cut filter in conjunction with GMB software, Bruce Fraser and Andrew Rodney also seem to favor the software (GMB) correction over the UV cut filter.

The spectro contains an illuminant that is projected onto a sample. If the illuminant contains UV, that UV gets transformed into visible light by the sample's brightener through a process known as fluorescence.
So the spectro without the UV cut filter will measure a sample (containing uv brighteners) more bluish as our eyes do.
Now according to Rodney in "Color Management for photographers", this will cause a blue color cast. Bruce Fraser and GMB on the other hand are talking about a possible yellow color cast.

In need some confirmation on this blue vs. yellow color cast:
In my opinion this difference beween blue vs. yellow cast is related to the used rendering intent.
When doing a relative conversion or a paper-gray perceptual conversion, such a profile will produce a bluish color cast (Andrew Rodney), as everything will be rendered vs. the measured bluish paper white.
An absolute colorimetric conversion or a neutral gray perceptual conversion will introduce a yellow cast (Fraser, GMB), as the profiling package will compensate by adding complemetary yellow.

Correct reasoning?

Herman
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Hermie
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« Reply #4 on: September 04, 2005, 11:15:49 AM »
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Thanks Jonathan.

Herman
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Hermie
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« Reply #5 on: September 05, 2005, 01:59:47 PM »
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The Eye-One has many advantages in itís so flexible. Spot (canít do that with DTP-70), Projectors (hope), Displays (nope). Light sources. But it does make you work for your profiles. The DTP-70 is ideal for someone that is making lots of profiles and need incredible speed. Itís shockingly fast.
I guess that coming from a colorimeter that only reads in patch mode, a scanning spectro is already very fast.

Herman
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Hermie
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« Reply #6 on: September 05, 2005, 01:15:23 PM »
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You can measure the paper and if the b* value is a negative, itís a good sign you might be finding OB in the paper.

Yes Andrew I know, I just got your book (page 210) ;-)

About Monaco Profiler, when you look at the measuring devices that can be selected from within Profiler, there's the eye-one and the eye-one UV. I know that only GMB uses software approach for detecting optical brighteners, but why then are the eye-one and eye-one UV listed separately in Monaco Profiler? Does it do something we don't know of?

What I really like about Profiler is the option to tweak the perceptual gamut compression.

In a thread on Rob Galbraith, Ethan Hansen wrote about the difference in measurement intervals between eye-one (10nm) and pulse (20nm + interpolation to 10nm). Do you thinks this is an issue in favor of the eye-one?

Herman
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